Marginal integrity between a prefabricated composite block and enamel, DEJ, and dentin

To evaluate the stability of the interfacial layer and leakage patterns between enamel, DEJ, dentin and three adhesive systems as demonstrated by either a dye or a silver nitrate technique to understand the marginal integrity of restored tooth substrates.

Extracted human molars were cross-sectioned to prepare enamel, DEJ and dentin surfaces. Areas with the DEJ aligned in the middle were restored with prefabricated flat composite blocks using either Superbond C&B (SB), Panavia Fluorocement (PN) or Variolink II (VL) cements. 7 restored specimens for each cement were prepared to investigate the interfacial layer after chemical challenge using SEM. Restored and control specimens for each cement were prepared for leakage tests by soaking either in 0.5% basic fuchsin or 50% silver nitrate solutions for 24 hours (n = 8). The penetration depth of tracer was measured using stereoscopy and a digital micrometer. SEM backscattered electron image and energy dispersive x-ray spectrometry were used to detect the location of the silver.

Prepared SB hybridized enamel, dentin and DEJ were stable against soaking in HCl followed by NaOCl solutions whereas prepared DEJ- and dentin-resin interfacial layers were degraded, detached and thinner than that of enamel in VL and PN specimens. No leakage was found at the enamel-resin interface for all cements and at the DEJ- and dentin-resin interfaces for SB specimens. VL specimens showed significantly greater leakage at the interface of dentin and DEJ than did PN specimens.